Chapter 11 Distributed Concurrency Control Chapter 11 Distributed Concurrency Control Concurrency control ensures the consistency and reliability properties of transactions. 111 SERIALIZABILITY THEORY The most widely accepted correctness criterion for concurrency control algorithms. A schedule S (also called history ) is defined over a set of transactions T={T1, T2, …,Tn} and specifies order of execution of these transactions’ operations. Two operations O x ij ( ) and O x kl ( ) accessing the same data item x are in conflict if one of them is a write. Conflicts are divided into r ead-write ( or write-read ) and write-write types. Two transactions are in conflict if an operation of one transaction is in conflict with an operation of the other by above definition. A complete schedule S T C defined over a set of transactions T={T1,T2,…,Tn} is a partial order 1

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